1. Field of the Invention
The present invention relates to a control and signalling device intended for protective switching applications, particularly relay-switches provided with a protective assembly capable of detecting faults (overloads or overcurrents) on each current path associated with a power pole, such device being actuated by a manual control member which may be in a `ON` position corresponding to closed contacts, a `OFF` position corresponding to open contacts and a `TRIP` position corresponding to the position after detection of a fault.
2. Description of the Related Art
On motor cut-out switches or relay switches the control and signalling elements are described as interlocks.
A motor cut-out switch or manual starter permits control of the poles either manually, or via a thermal and magnetic triggering assembly which provides a protective function. When an electrical fault is detected on one of the line phases, the thermal or magnetic device of the corresponding phase triggers the opening of contacts by means of a shared interlock. The latter may further be manually actuated by a manual control.
A relay switch combines both a contactor and a circuit breaker. It comprises a magnetic and/or thermal trigger unit and an electromagnet which controls the poles to ensure the contactor function. The motor cut-out switch or manual starter mentioned earlier includes similar means to activate its contacts but lacks an electromagnet.
An interlock relay switch permits control of the `ON`, `OFF`, `TRIP` and reset functions and it also make the position of the contacts visible through the manual position of the control button of this interlock.
Numerous interlock devices exist but they are often complicated, costly, bulky, and of complex and delicate operation.